def fibonacciSum(n):
    num=0
    n>0
    if n==1 or n==2:
        return 1
    else:
        return fibonacciSum(n-1)+fibonacciSum(n-2)
def fibonacciSum(n):
    for i in range (1,n+1):
        num+=fibonacciSum(n)
        return num
n=eval(input("输入一个值:"))
print("斐波那契数列的前{}项的总和是{}".format(n,fibonacciSum(n)))
